Ultra short wave electron discharge device system



Jall- 20, 1942 H. J, R, voN BAEYER l 2,270,777

ULTRA SHORT WAVE ELECTRON DISCHARGE DEVICE SYSTEM Filed July 3, 1940 HLW Gttorneg short waves in magnetron tubes.

Patented Jan. 2l),v` 1942 ULTRA SHORT WAVE ELECTRDN DISCHARGE DEVICE SYSTEM Hans Jacob Ritter von Baeyer, Berlin, Germany,

assignor to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, corporation of Germany Germany, a

Application July 3, 1940, Serial No. 343,757 In Germany April 6, 1939 7 claims. (ci. 17e-1715i The invention relates to an arrangement adapted to the amplitude modulation of ultra Over earlier arrangements of this kind the circuit organization here disclosed offers the advantage that disturbing frequency modulation is avoided. It is known that in modulating one of the operating potentials of a magnetron tube essentially the frequency is altered and only in a subordinate manner also the amplitude of the produced oscillation Circuit organizations are also feasible in which only the frequency may be modulated, but not the amplitude. But the reverse problem, namely to insure amplitude modulation pure and simple, has not yet been solved in a satisfactory way, if such schemes as double modulation which are unsuited for practical purposes and in which the undesired modulation is neutralized by modulation in the opposite sense are disregarded. Pure amplitude modulation is brought about by controlling the emission of the cathode. However, this procedure cannot be considered in practice with the, conventional type of magnetron tube for the reason that the lament is far too sluggish to use rapid variations of the heating current for modulation.

To obviate these diiliculties, the invention uses in a magnetron tube a focussed electron pencil as the source of electrons. The latter are shot laterally into the anode cylinder through a diaphragm or stop maintained at a constant potential, the pencil prior to its entry into the anode cylinder being so controlled that the number of entering electrons varies at the rate and rhythm of the modulation, though not to any substantial extent the speed thereof.

It has been suggested in the earlier art to arrange the cathode of a magnetron tube laterally in respect to the anode cylinder, to the end of avoiding extra or additional heating effects. However, these known arrangements do not work with a focussed electron pencil. Neither has it been suggested in the prior art to modulate the emission of such a laterally disposed cathode. What earlier arrangements likewise lack is the diaphragm or stop between cathode and cylindrical anode which insures perfect decoupling of the two systems and which constitutes an essential feature of this invention.

The invention shall now be explained in more detail by reference to the appended drawing, wherein Figs. 1, 2 and 3 show, by way of example only, three embodiments of the present invention. Fig. 2a is a front or rear view of a detail of Fig. 2.

Referring to Fig. 1, H denotes a cathode (heater) and W is a Wehnelt cylinder known in the art. The concentrated or focussed electrons issuing therefrom ily through the diaphragm B which is kept slightly positively biased relative to the cathode and they then reach the magnetron system. The latter may be of any convenient form of construction, say, with split anode A. The anodes are associated with the oscillatory circuit L and they are subject to a high positive biasing potential relative to the cathode. At the end opposite the cathode may be mounted a collector electrode F which is impressed with a feebly positive potential. For the purpose of modulation of the oscillations generated in the anode system, the focussing of the pencil is altered by acting upon the biasing voltage of the Wehnelt cylinder or shield by the aid of the transformer T. 'I'he result is that the number, though not the velocity, of the electrons passing through the stop B will be modulated. If the velocity were to cha'nge to any appreciable degree, this would mean frequency modulation. However, it is to be noted that slight variations of speed will not cause any trouble as long as they are small in contrast to the ultimate electron speed produced by the anode voltage.

To focus and iniiuence the density of the electrons in the pencil or beam, recourse may be had to any of the electrode systems known in the art of electron-optics. The ways and means illustrated in the drawing are simplied for the sake of clearness, and they may be further developed or modied at will.

The basic idea of the invention is particularly advantageous in the case of magnetron systems, the axial length of which is reduced and in which, therefore, the requisite number or volume of electrons is producible only with great diiculty by means of a standard axial cathode. 'I'his is shown in Fig. 2 in which the magnetron system as already suggested in the art, consists of a metal plate or disc M, the central opening E thereof constituting the discharge space, while the outer bore holes B' represent the various oscillation circuits. (Note Fig. 2a showing a front or rear view of the disc M.) As to the rest, this modulator device corresponds fully to that shown in Fig. 1.

In the arrangements of Figs. 1 and 2 the magnet system, to produce the requisite magnetic field, has been omitted for the sake of simplicity of illustration. In fact, this eld may be generated in any desired manner at all, for instance by a solenoid. Ways and means adapted to obtain particular intense elds are shown in Fig. 3. This embodiment comprises pole-shoes Pi and P2 which extend to points close to the anode cylinder A. In order to avoid the necessity of `preferable to impress the modulation potential upon a separate diaphragm Bm rather than upon the pole-shoe, said diaphragm Bm being mounted in front of the diaphragm BA corresponding to the one shown in Fig. 1. The collector electrode F may be placed directly upon pole-shoe P2 with interposition of an insulation disc, as indicated at J.

The invention is not restricted tothe exemplied embodiments here shown. Broadly, the basic idea of the invention is to produce, in a magnetron tube designed for ultra-short waves, modulation by pure intensity control action in a cathode ray pencil forming the source of the electrons of the tube system. But by convenient choice of the various working voltages, the generation of the oscillations itself may correspond entirely to the generation of oscillations in conventional magnetrons. Modulation is largely free from inertia so that it is practicable up to the highest modulation frequencies, that is, frequencies as occurring, for instance, in television work. 'I'his applies not only to the pencil control or modulation as described, but also, for instance, to transverse control interiorly of a diaphragm.

What is claimed is:

1. An ultra short wave electron discharge del vice system comprising an evacuated container containing therein in the order named a. cathode for producing a stream of electrons, a focussing shield for said cathode, an electrode having a central aperture for the passage of electrons therethrough, a pair of anode segments, and a y collector electrode, a load in the form of an oscillatory circuit connected to said pair of anodes for deriving energy from said system, means for maintaining said focussing shield ata negative potential relative to said cathode, and a source of modulation potential coupled to said shield.

2. An ultra short wave electron discharge device system comprising an evacuated containerI containing therein in the order named, a cathode for producing a stream of electrons, a focussing shield for said cathode, an electrode having a central aperture for the passage of electrons therethrough, a pair of anode segments, and a collector electrode, a load in the form of an oscillatory circuit connected to said pair of anodes for deriving energy from said system, means for maintaining said focussing shield at a negative potential and means for maintaining said anodes at a positive potential relative to said cathode, and a source of modulation potential coupled to said shield.

3. An ultra short wave system having, in combination, a magnetron device comprising an evacuated container containing therein in the order named, a cathode for producing a stream of electrons, a focussing shield for said cathode, an electrode having a central aperture for the passage of electrons therethrough, a pair of anode segments, and a collector electrode, means for producing a magnetic eld for said magnetron device, a load in the form of an oscillatory circuit connected to said pair of anodes for deriving energy from said system, means for maintainmg said focussing shield'at a negative potential relative to said cathode, and a source of modulation potential coupled to said shield.

4. The combination with an ultra short wave electron discharge device magnetron oscillator comprising an evacuated container containing therein in the order named, a cathode for producing a stream of electrons; a focussing shield for said cathode; a diaphargm electrode having a central aperture for the passage of electrons therethrough; a cylindrical anode structure having a centrally located aperture for the passage of said electrons, and a collector electrode; means for maintaining said focussing shield at a negative potential, said diaphragm electrode at a constant positive potential, and said anode structure at a positive potential all relative to said cathode; means for producing a uniform magnetic field directed along the axis of said discharge device; of means for modulating the amplitude of the waves produced by-said oscillator, said means including a modulating source of signals connected to said focussing shield.

5. A system in accordance with claim 4, characterized in this that said anode cylinder comprises a metallicplate having a plurality of holes around the center aperture, the surfaces of said holes constituting oscillation circuits.

6. An ultraA short wave magnetron system comprising an evacuated container enclosing therein, in the order named, a cathode for producing a stream of electrons, a cylinder surrounding said cathode, an electrode having a central aperture for the passage of electrons therethrough, an anode structure having an oscillatory circuit coupled thereto, and a collector electrode, means for maintaining said cylinder at a negative potential and both said centrally apertured electrode and said collector electrode at a positive potential relative to said cathode, means for producing a uniform magnetic eld directed along the axis of said stream of electrons, and a source of modulating potential coupled to said cylinder.

7. An ultra short Wave magnetron system comprising an evacuated container enclosing a cathode for producing a stream of electrons, an apertured element adjacent said cathode for enabling modulation of said stream, an electrode having a central aperture for the passage of electrons therethrough, an anode structure having an oscillatory circuit coupled thereto, and an electron collector electrode, means for maintaining said element at a negative potential and both said centrally apertured electrode and said collector electrode at a positive potential relative to said cathode, means for producing a uniform magnetic eld directed along the axis of said stream of electrons, and a source of modulating potential coupled toA said element.

HANS JACOB RI'I'IER voN BAEYER. 

